Abstract : The significance of this research to the Air Force lies in the following three conclusions: (1) It is not possible to improve upon the high frequency amplifier performance of existing transistor types of developing a Coherent-Beam-Of-Light-Transistor (COBOLT), that is, a transistor that employs an injection-modulated injection laser as emitter; (2) A COBOLT might be of considerable interest as an electronically tuneable microwave resonance element; (3) Higher frequencies than by injection modulation might be achievable by electrooptic modulation of injection laser light, with somewhat uncertain noise properties of the device. The objective of this research had been to study theoretically the high-frequency properties of a COBOLT, especially to check the expectation that such a device might make possible a drastic extension of the frequency range of transistor amplifiers.